Tandem multiplane



Oct. 6, 1925.

T. R. M MECHEN ET AL TANDEM MULT I PLANE Filed June 6, 1925 2 Sheets-Sheet 1 INVENTOR-S Thomas EMaaMecken fllemnoerjflemirz.

ATTORNEY.

Oct. 6, 1925.

T R M MECHEN ET AL TANDEM MULTIPLANE Filed June 6, 1925 2 Sheets$heet QM {I I %M .4 TTORNEY.

, planes.

Patented Oct. 6, 1925.

UNITED STATES PATENT OFFICE.

THOMAS B. MAGMEGBEN AND ALEXANDER KLEMIN, OF NEW YORK, 11'. Y.

TANDEM HULTIPLANE.

Application filed June 6, 1925.

To all whom it may concern:

Be it known that we, THOMAS Rr'rnnn- FORD MACMRCIIEX and Auaxarvmzu Kmzzuin, citizens of the United States of America, residing at New York city, in the county and State of New York, have invented certain new and useful Improvements in Tandem Multiplanes, of which the following is a specification.

This invention relates to aeroplanes and it. has more particular reference to that type now commonly known as monoplanes as distinguished from others involving superposed air planes in spaced relation.

In the construction of large aeroplanes, it is theoretically demonstrable that with increasing size the weight of the structure as a percentage of the gross weight increases appreciably. If a machine is large enough this percentage increase in the weight of structure becomes so great that even refinement in design possible in large machines-is insufficient to affect the increase in weight. Therefore a point is ultimately reached where the machine becomes so large, and the structural percentage of weight is so great, that when the weight of the power plant is added to the structural weight, no useful load remains: .useful load representing capacity for adequate incl, 1iasscn; ;e rs,

baggage and so forth.

' Designers of aircraft have endeavored to meet this size limitation by departing from the most eflicient type of machine at Jresent extant-the monoplancby using biplanes, triplanes and multiplanes.

Even with the adoption and use of iii-planes or tri-planes the weight limitation must be reached with a suiliciently large machine; furthermore, such machines are characterized by a marked decrease of aerodynamic eiiiciency. Again the use of quadruplanes has never been seriously contemplated by reason of the aerodynamic inefliciency of such an arrangement of Again, it has been suggested that a system of tandem or follow planes might overcome the above referred to weight limitation.

Accordingly it may be here stated that an important object of our invention is to overcome the recited objections by providing a novel system of tandem lanes s6 correlated and relatively positioned as to provide an Serial Kc. 35,340.

heavier than air flying machine, capable of transporting a pay load on economical and profitable. lines.

Accordingly we have devised a novel tandem multi-plane system of aerofoils so arranged that the pay load is better distributed relative to a larger area or number of wings, each said wing having a comparatively smaller s ran as compared with monoplanes hitherto adapted to lift and carry the same load. A further advantage of our novel system of aerofoils is that the weight of the Wings is reduced, while it is feasible to distribute the load along the entire length of the machine whereby the structural light ening of the fuselage or body is attained.

Again, our novel tandem multi-planc system of acrofoils precludes the tremendous concentration of forces locally as is present with bi-planes or triplanes hitherto suggested wherein the whole lift of the entire wing system is transmitted to two points on either side of the fuselage or body. Accordingly it may be correctly premised, and we have succt' ssfully proven as hereinaft r set forth, that a tandem type of multi-plane 03ers the correct solution to the problem of heavier than air craft of larger dimensions capable of transporting a pay load upon successful lines. In other words we have successfully provcn b Y exhaustive tests that our novel system 0 relatively positioned aerofoils overcomes all the present disadvantages inhcring to monoplane, biplane, triplane or quadruplane types. As a natural sequel we are enabled to construct heavier than air craft of no larger over-all dim nsions than now obtains with a lighter percentage of structural Wei ht, thereby augmenting the pay load and rendering them more profitab e commercially.

Nith the foregoing and other objects and inherent advantages in view, our invention may be terselv defined as consisting essentially in so isposing the respective aerofoils of a tandem multi-plane as to ensure the maximum carrying capacity while attaining a degree of flying stability hitherto unknown.

In order that our invention may be readily comprehended by those acquainted with aero-dynamics, we will now describe the same by reference to the amompanyixig sheets of diagrammatic drawings. These drawings t pity tandem multi-plane combinations em odying the essential features of our invention, and in the several views corresponding elements are designated by like characters of reference, while the subjoined claims serve to point out in succinct terms the features we believe to be novel and therefore patentable over prior art.

Figure l-is a diagrammatic illustration showing the action of a wing unit in deflecting the air stream so that the lift force on a succeeding wing is deflected over from the vertical.

Fi 2-is a view showing thd' preferrefi il isposition of three wings arranged in accordance with our invention.

Figure 3-is a similar diagrammatic view illustrating a four win combination embodying our improved p acement svstem.

' Figure 4 is a slightly modified showing of the arrangement illustrated by the preceding view.

Figure 5-is a further typical example of a four wing combination on what may be termed definite serial sequence lines.

Figure 6--is an extension of the form of our invention shown in F'gure 5 to an extended air craft; and

Figure 7 is an outline of the showing illustrated in Figure 3, as applied to a flying machine along successful pay load commercial lines.

In the following description it is to be clearly understood that the several views while diagrammatic and devoid of structural details are positively indicative of the pro posed relation of the respective elements or units.

Referring firstly to Figure 1. a pair of aerofoils or wings are respectively desig nated by the numerals 10, 1.1. the former being the leading one, while the air stream lines thereover are characterized by fine lines 12. Now, it will be clearly apparent to anyone but slightly acquainted with aerodynamics that the air stream cncmmtcrcd by the rear wing 11 is exerting :1 downwash or drag thereon as indicated by the arrow 13. Incidentally this drag or down- Wash from the front Wing 10 affects the rear wing disadvantageously, and such effect is intensified when multiple tandem wings are employed. Knowing this inherent difliculty we have by systematic wind tunnel experiments and investigation so dis posed the wings of our novel tandem multiplanc combination as to evolve a machine, practical structurally and possessing the requisite aero-dynamic eiliciency, by largely-if not entirely eliminating all downwash interference.

In the typified combinativns of Figures 2-4 it is to be noted that assuming the chord dimension as c the relative dispositions may be capitulated as follows Figure 2, illustrates three wings 14, 15 and 16 with a relative disposition as follows. The second wing 15 is located at a three chord span in rear of the leading wing 14 with a one-and-one-half chord drop; where as the trailing wing-16 is located at a three chord interval in rear of the second wing 15 with a three chord elevation relative thereto, or a one-and-one halt chord location above the leading wing 14;. The win 16 or its counterpart is hereinafter referre to as the parasol wing, in that by virtue of its relation to the other wings it is mainly functional as a sustaining unit ensuring flying stability both laterally and longitudinally of the machine.

In Figure 3, we have shown the three wings 17, 18 and 19 as disposed along identical lines with the wings 14; 15 and 16 of Fi ure 2, but with the addition of a tail wing 20 located in the rear of the wing 19 at a span of three chords and drop of one-and-oue'half chords relative thereto. Incidentally it will be remarked that the tail wing :20 is disposed co-planal with the leading wing 17.

Figure 4, is along the lines of Figure 3 with. the exception that the parasol wing 20 is transposed relative to the lover wing 18, accordingly the same reference charactors are applied thereto and further elaboration omitted.

Turning now to Figures 5 and 6, we will first of all outline the relation of the wings in the first mentioned view which illustrates four wings 21, 22, 23 and 24. It is to be particularly observed that the wings 21 24 are on the sinus plane, whereas the wings. 22, 23 are. located at three chord intervals with a successive drop of one-and-one-half chords relative to the leading wing 21, whereas the altitude relation of the wings 23, 24 is three chords.

Figure 6, typifies a succession of wings 25, 3.6, 27 relatively spaced at three chord intervals with stepped successive drops of nnc-aml-one-half chords, it being particularly noteworthy that the respective wingsof each succeeding set of three are complenlentarily disp sed. This disposition of the wings 25, 26, 27 affords a structurally stable combination for large aircraft alon commercial lines and is devoid of longitudinal interference.

Turning now to an explanation of the reasons for the specifically recited combinations of wings above set forth, it is to be nolcd that heretofore designers of heavier than air flying machines and more particularly tandem planes have been ignorant of the acre-dynamics involved. Furthermore, while vaguely recognizing there existed interference between a forward and a rear plane, few attempts, if any, have been directed to an investigation of such interincense ferencc, or to the evolution oi means to avoid said interference. i a natural result, the flying machines so far suggested have all been more or less impracticable for pay load usage by virtue of the inter ference above stated, and the consequent acre-dynamic ineificiency. Another funda. mental reason for the induced drag in machines previously exploited is the action of the tip vortices. Such induced drag is a disadvantage in the case of a monoplane, e biplane or a. triplane not disposed in tandem, while it is of still greater consei uence in the case of airplanes having wings osed in tandem.

hus it has become acknowledged that the vortices of a forward wing caused a pronounced downwash on the following wing, therefore such following wing or wings no longer traverses an air stream which is in the same direction as the air stream. encountered by the forward plane but. it is operating in a dmvnwardly directed air stream. Applying the foregoing to the showing of Figure 1, it will be apparent that the lift force on the wing ll is acting perpendicularly to the downwardly deflected air stream 12, or in other words obliquelv to that exerted on the wing 10. The lift force therefore new has a component which is in a direction of drag or resistance, as indicated by the arrow 13. Such drag or resistance in at combination of win s-mot aerodynamically correctly related or disposed-is obviously greatly increased.

In previously suggested tandem planes claiming to avoid drag iutcrferemse. och claim has not been substantiated by ctperh ments and is purely hypothetical.

in our initial experiments on tandem p. nes in the Wind tunnel under :1 eady wind and fUI'l'tS measured. to simulntc actual flight conditions, we found 11ml the known mndcm biplane combinations were iu'ipractirnble as the vnlmes of lift coell'icicnts wore low and the values of drag greatly incmused. The resultant eiliciency of lift over drag values were so low hat we found it would be impossible to ii ch machines without n disproportiouute expenditure of pom 1', end if capable of flight at all no useful or pay loud could be accommodated and carried. its a result of an extensive series of tests We discovered the true principle of tandem plane arrangement, and the useful v combinations illust uul. in Figures -7 are of a proven Cllill'lhftfil to produce entirely practicable and profitable nnichines. Accordingly, it will be understood that the correct disposition of fOllQA'lIlg wings, such as l5. 1.6 or 1R 1.9, 20 relative to the respective front wings 14, 1? is dependent on rearward t'lisplocement, and also displacement in a; verti al direction. Hence the rearward and vertical displacements of the planes 15,

11".) or 18, 1.). must, for practical reasons he as small as possible in order to provide a compact machine having neither too great an overall length and height.

Our experiments :ilso proved the admin ,all of our wing combinations as provided with sheltering or tip fins 28, but it is to be distinctly understood that we do not confine ourselves to their use as we have obtained satisfactory efiiciency results without them. consequent upon our tests we have definitely discovered that in order to place 21 tandem wing 15, 18in the correct position where it is not seriously interfered with by the respective front plane 14, 17 it must be disposed at a distance to the rear thereof of three chord lengths, and a distance downward of ()llQ-filld-ODG-lldlf chords. Such n disposition we have found places the wings 15, 18 in a position where the interference from the front wings is so nuiterinlly re duced that the elliciency of said wings is raised to practicable values. At the some time we found that placing the tandem wings 15, 18 in excess of three chords length spun along the line of flight, and at more than oneend'onwhnif chords vertical drop relative to the front wings 14, 17 did not in crease the elllcicnry to any appreciable degree. Hence it will be apparent any ma.- tcrizil excess of the relative chord spans would not be of e. practicable character.

Another very important factor discerned as an outcome of our experiments is that the placement of u tandem wing to the rear and above the lending wing. is not etlicient, hence negative stagger as it is noiv known in 1h 2 art is inadvisable.

\dvanwnm-nt with our series of tests dis closed that where three wings such as 14, if) and 16 were arranged. as shown in Figure with the trailing wing 16 utlthc hereinbefore stated negative stagger. ull delrimelr tel effects incident to such negative placement were eliminated and substantially normal values obtained for the new-dynamics of the third wing 16. By a similar process of test and investigation we evolved the cor rect position for a fourth Wing, such as 24 in Figure 5or 19 in Figure 4-the same being located at three chords in rear of the third wings 23, 18, with a respective three chord and one-nnd-one-half chords elevation relative thereto; or in an efficient position of positive stagger in both examples. Continuing our tests we finally discovered that where tandem planes 25, 26, 27 were, arranged in serial sequence of sets of three. as shown in Figure 6, each said set should be related with a positive stagger. Hence it loo will be apparent that by the set forth shillful disposition of tandem multi-planes we have secured all the advantages of a follow plane combination and attained a high aerodynamic efliciency. Obviously the arrange ment of planes set forth may be extended to live or more monoplane wings disposed in follow plane stvle.

Figure 7, illustrates the application of our improvements to an extended fuselage or body 29 with a series of Wings 30 mounted relative thereto along the lines of the showing in Figure 3, with suitable aeronautical motors 31 carried by the forward and two trailing planes. This example is by way of illustration of the practical pos sibilities of our in'iprovements commercially and it will be obvious the body 29 may be appropriately divided for passenger and freight acconunodatioin with ample leeway for power control, steering and other equipment as well as adequate fuel storage.

The results of our series of tests are briefly tabulated below :(l) A single monoplane Wingmaximu1n Ky .0029 L/Il 14.2. (2) Four wings with tip fins as arranged in Figure 3-1naxiinum Ky 110264 and maximum L/D, 8.8. (3) Four wings with tip fins as per Figure f ---n1uxiuuun Ky .00249 and maximum 10.45. (1) Three wings as per lcadinu :uit of Figure 6n1aximum Ky .0021? and maximum li /D 10.75. (5) Six wings as per two leading units of Figure tl-nuxximum Ky .UOQS-t and maximum L/D 8.7.

Still further we discovered that the pro vision of the fins 28 at the tip of the re spective Wings was always beneficial in that it invariably increased the wing ellicieucy, and diminished the downwash on the following Wing. Such tins. lunvcver, form the subject matter of our ctr-pending application for patent filed the 16th day of ll'larch, 1925. under Serial Number lfu'i'i'fl, and are merely re'fcrredto herein as enhancing the cflicienoy of our present invention, and hence highly desirable in the production of a profitable m'aehine.

Another feature noteworthy as a result of our exhaustive cxporinu ntation is that owing to the fact that dou'nwush is not entirely eliminated it may be found advanta genes to vary or modify the angle of incidence of the tandem Wings relative to the leading one disposing them at progressively larger angles from the front to the rear. The ta den] wings are thus placed at larger effecti e angles of incidence than would otherwise be the case due to the downwash and the cfliriency is increased thereby. A concrete example using four wings with the first leading one at zero do grace, the second at two degrees, the third at four degrees, and the fourth at six degrees disposed as shown in Figure 3 gave 1,5:se,5eo

the following efiiciency result--maximum Ky 110284 and maximum L/D 936.

From the foregoing description and incorporated test data it is thought the present invention will be clearly apparent While the advance acre-dynamically in the art is so palpably obvious as not to require furthe:- elaboration herein. However, We de sire it to be distinctly understood that we lay no claim broadly to any bi-or-niulti follow plane system, but what We do claim, and desire to secure as our due reward, is a tandem multiplanc combination of acre foils whereby a pay load may be profitably transported with a higher factor of dying stability and safety than has heretofore been obtainab e.

Having described our invention what We claim isc-- 1. A tandem multi-plane embodying a succession of acroioils at substantially three chord intervals and substantially one-andone-halt descending altitudes from the lead ing to the roar aero foils.

2. A tandem multi-plane embodying three successive aerofoils disposed at three chord intervals with a descending altitude relation of one-and-onul'ialf chords from the front acrofoil to the rear one.

3. A tandem inulti-plane embodying a snow sion of aerofolls disposed at three chord intervals longitudiuallv and one-andene-half chord descending relation from the forward aero'loil.

4. A. tandem multi-plane eiiihodying e.- snccession of aerofoils disposed at three chord intervals longitudinally and one-andone-halt chord descending relation form the forward aerefoil, and the rear aerofoil rails ed at a similar elevation above the plane of the lending acre-toil.

A tandem multi-plane comprising successive series of aerofoils, each said sevies embodying units disposed at three chord intervals longitudinally and one-antiquehalt chord descending relation.

6. A tandem multi-plane comprising successive series of aerofoils, each said se" ries embodying three units disposed at three chord intervals longitudinally and onenucl-onohalf chord descending relation.

7. A tandem multi-plane comprising a succession of aerof'oils at three chord intervals and 0ne-and-0nc-half chord descending relation from front to rear of the plane and at a progressive angle of incidence with respect to the leading aerofoil.

8. A tandem multi plane comprising a succession of aerofoils at three chord intervals and one-and-one-half chord descending relation from front to rear of the plane and at a progressive angle of incidence with respect to the leading aerofoil, the trailing unit being at a oneand;one-half chord elevation above said liladi'il am'nf ill) 9. A tandem multi-plane comprising half elevation. above said leading aerofoil. a sqecession of aerofoils at three chord in- In testimony whereof We aifix our signa- -termlemul one-'and-one-half chord descendtures to this specification the third. day of 10 ing relation from 'front to rear of the plane June, 1925. r 5 and at a progressive angle of incidence with respect to the leading aerofoil, one of the THOMAS R. MAoMECHEN. intermeiate units being at a one-and-one- ALEXANDER KLEMIN.

In testimony wherwf We affix our si June, 3925 MAUMECHE N. JEIEZANDER KLEMIN.

Certifimte at Canadian.

H [S hereby cettifed that Letbes's Patvnt N0. 1.556560, gruniiad October 6. 1925. rpm: the applirruirm 0f Thumns R. Maui-Mvchen and Alexander Klemin, of Now z'm-k, N, Fm; an improvenwnt in 'Pandmn Multipianes," were erroneously islsmul to mid Mm-fvlechvn and Klemin as joint owners, Where-as said Letter s iuiunt simuid have been issued to Tiwzrzne H. .Urzciimhen as sole owner of said inwntnon, as shown by the rewards-2 of assignments in this ol'fice; and that the said i'n-ttm-b Patent shrmid he read with this correction Therein that the same may 0011- fw 1 in the wizard of the (153 in $318 Patent gum} and .wafed this 31] day (sf November, J's 1925.

5%. KARL FENNING,

A mz'ng Ca-mmissiow of Patemfe comprising half elevation above said Ending aerufoil.

tures to this s euificatiion the third day of 10 Certificate 0f Oarroctiom 11 Is hereby cmlifienl that, Letters Patent No. 1556,5560, granted October 6. 1925 upun the applirutiun of Thomas R. ManMnchen and Alexander Klemin, of New York, N. Y., for an improvement in Tandem Multiplanes, were, erroneously issued to said MacMechen and Klemin as jnintvowners, Whereas said Letters Patent should have ban issued to T from 1a H. MacMee/oen as sole owner of said invention, as shown by the records of assignments in this oflice; and that the said Letters Patent should be read with this correction thereinthat the same may eon form to the record of the vase in the Pcdent (mice.

Signed and sealed this 3d day of Novemben A D. 1925.

[am] KARL FENNING,

A sting Commissioner of Patents, 

